Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1149 AM EDT Mon Jun 04 2018
Valid 12Z Thu Jun 07 2018 - 12Z Mon Jun 11 2018
...Heat to continue for the Desert Southwest to the south-central
U.S...
...Pattern overview...
Upper ridging is forecast to remain anchored over the southern
Plains late this week into next week with troughing on either side
of the CONUS. This will maintain well above average temperatures
for the southwest and southern Plains (widespread 100s) with daily
record max temperatures likely for some areas. A significant
trough will attempt to push into the Pacific Northwest late in the
period which will introduce cooler than average temperatures to at
least Washington/Oregon. The north central and eastern portions of
the lower 48 stand the best chance of rain along a wavy frontal
boundary as areas of low pressure exit the east.
...Model guidance/predictability evaluation/preferences...
The recent GFS/ECMWF runs paired well with the ensemble means with
the well-forecast longwave pattern. Differences expanded south of
the Gulf of Alaska with the incoming trough next week but a blend
among the models/ensembles offered a good starting point.
Elsewhere, the UKMET/Canadian offered some corroboration to the
GFS/ECMWF to start but otherwise departed from that consensus by
about Friday. Smaller scale uncertainties exist within the pattern
but most are unresolvable at this lead time (e.g. "ridge rollers"
through the Plains).
...Weather highlights and hazards...
The heat wave will be the main story with readings 100 degrees
plus anywhere from the Desert Southwest eastward along the Mexican
border into the state of Texas. Departures from climatology should
be around 10 degrees although slightly higher numbers can be found
farther north into the remaining Great Plains states and into the
Intermountain West/Rocky Mountain chain. Widespread 80s and 90s
are likely over these locations (+10 to +15F anomalies). Regarding
cool spots, Thursday should prove to be near or slightly below
climatology across the East Coast with such conditions persisting
into the weekend across Florida given immense cloud cover and
rainfall. Elsewhere, deep upper troughing over the Pacific
Northwest will hold temperatures around 5 to 10 degrees below
average from Saturday onward.
It should remain intermittently wet over the southeastern U.S.,
particularly Florida, given a stagnant upper trough/weakness in
conjunction with an anomalous moisture feed. Back toward the
middle of the country, multiple convective complexes are likely to
erupt north of the ridge with propagation downstream toward the
mid-Mississippi Valley and into the Great Lakes/Ohio Valley. SPC
has highlighted the Northern Plains on Thursday for some organized
severe weather but bouts of heavy rainfall will persist into next
week. Elsewhere, it should prove to be quite wet over the Pacific
Northwest given the deep cyclonic flow overhead. Strong forcing
with the trough and eventual frontal passage could spread
considerable early/mid-June precipitation to the region.
Fracasso/Rubin-Oster
WPC medium range forecasts of 500 mb heights, surface systems,
weather grids, quantitative precipitation, and winter weather
outlook probabilities can be found at:
http://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
http://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
http://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
http://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
http://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4